New antibiotic may block toxins from bacteria

CHICAGO (Reuters) - In a new approach to serious stomach bugs like salmonella, U.S. researchers said on Thursday they have developed an antibiotic that works by blocking the bacteria's communication signals, keeping it from releasing toxins that make people sick.

"The sensors in bacteria are waiting for the right signal to initiate the expression of virulent genes," Dr. Vanessa Sperandio of the University of Texas Southwestern Medical Center, said in a statement.

Instead of looking for new ways to kill the bacteria, like most antibiotics, Sperandio and colleagues found a compound -- LED209 -- that simply disarms them.

"Using LED209, we blocked those sensing mechanisms and basically tricked the bacteria to not recognize that they were within the host," said Sperandio, whose study appears in the journal Science.

Millions of potentially harmful bacteria are present in the body, but without the proper chemical signals, such as from a hormone, they simply pass through the digestive tract.

In prior studies, researchers at UT Southwestern identified special receptors on a diarrhea-causing strain of Escherichia coli that receive signals from microbes and hormones in the intestine that activate the bacteria.

In the latest finding, Sperandio's team identified a chemical, LED209, that blocked sensors on bacterial cultures of E. coli, salmonella, and Francisella tularensis, which causes tularemia or "rabbit fever."

It also kept mice infected with salmonella and F. tularensis from getting sick.

"This study demonstrates that LED209 has promise in fighting at least three pathogens, and likely many more," Sperandio said.

Because the new compound does not kill the bacteria, the researchers think it would not be easy for bacteria to develop antibiotic resistance, a problem common to most other antibiotics.

(Reporting by Julie Steenhuysen; Editing by Maggie Fox and Sandra Maler)